Coolant Test?

I try to test my coolant pressure but system will not hold pressure.I took all plugs out they all have grey look so I did compression test and seems all cyl. have 160-170 psi.Where can air go from the coolant system and what can be causing the problem?The car not running hot.THe compression test was done cold and throttle was not open,

How did you test it? And are you talking about your hotrod?

With a tester that goes in place of radiator cap and pumps up.Yes it my hotrod.....

If you're testing it because you're losing water , I'd pull the spark plugs and the oil drain plug. Pressure it up a little and let it set for a while. If you don't get any water out the drain plug hole , crank the engine and see if it blows out one of the plug holes.

Dave C. wrote:If you're testing it because you're losing water , I'd pull the spark plugs and the oil drain plug. Pressure it up a little and let it set for a while. If you don't get any water out the drain plug hole , crank the engine and see if it blows out one of the plug holes.

Not using water

Put water in it and test it.

Dave C. wrote:Put water in it and test it.

I did it will not hold pressure.I try the tester on another car and it works fine.

Necks on the radiators are different ?

I just thought of something that I did not do.If I did not plug off the overflow tank it could pushing the air in the overflow?

Plugging off the over flow should not matter or have to be done. The rubber gasket on the tester should seal against the bottom of the radiator neck. Measure the depth from the radiator it worked on and compare it to the one on your hot rod. Some radiator necks require an extra rubber washer on the tester or a thicker one to seal properly.

So what should be going on if engine has no coolant pressure

With no water in the system during the test shouldn't you be able to hear any escaping air pressure as you try to pressurize the system?

Another way to check head gaskets, combustion chambers, and block, fill system with water, back off all rocker arms, roll the pistons down to BDC, then with a spark plug adapter, apply air to each cyl and see if you get air bubbles in the radiator, repeat on each cyl. That should eliminate possible cracks in the heads, and cyl walls, or leaking head gaskets.

Have you had the heads ported? Is it possible you have a pin hole in one of the ports?

He says it's not using water, he just can't pressurize the system. The tester works on other cars, so I supect poor/no seal at the filler neck...maybe leaking into the overflow tank.

John, have you listened carefully at the filler neck and overflow while trying to pressurize?

Have you went back and checked all hose clamps an made sure they not leaking if you are check the system dry get a spray bottle and use some soapy water and spray everything good and watch for bubbles.

Checking system full of water.

maverick wrote:He says it's not using water, he just can't pressurize the system.  The tester works on other cars, so I supect poor/no seal at the filler neck...maybe leaking into the overflow tank.

John, have you listened carefully at the filler neck and overflow while trying to pressurize?

This maybe the problem but with the kit I got it does not have extra seal.

Well I pulled engine to tap screw in freeze plugs and when I was taking collector off passager side I seen it full of oil.So I looked in each header and all looked be same with no oil in them. Make me believe oil coming from valve covers thru crankcase evac system.What could cause oil to be force out valve cover into collector?

With an evac system, it's not unusual to notice a little bit of oil in the headers after shutdown, since the trickle from the evac hose won't be burned away. I get a little bit of smoke at startup for that same reason. Otherwise, if the engine runs good and doesn't smoke or use oil, I wouldn't worry too much. You might check to see if the valve covers are baffled at the evac holes, though.

Oh yeah...and a compression check might put your mind at ease.

Maybe I missed something , but not running hot , not using water , what are you worried about ? is it running strange at all ? And do you run mufflers ? I'm asking that because on my street car with a evac system it had oil dripping out of the band clamps and made a smoker , unhooked them and it was fine a few days later.

After the freeze plug came out and i like to lost no telling what I started thinking about alot of things.First was could it be building pressure and it pop out.Then if I had install them wrong and how I could make sure it want happen again.So at that point i started doing test on engine which ran good.First test was coolant test which got me all hell cause I could not get it to hold pressure.2 test was compression test which seem be fine.Maybe it was just a bad install and pressure test was not seal off but after in my mind of being blessed i want do everything in my power it solve problem.So i pulled engine to install screw in freeze plugs and pulled heads check head gaskets leaks plus head.Might be over kill but I believe in it fine have a problem but do fix it or give it best shot.

Ok I see , that's right the freeze plug thing happened I remember now, well its not going to pop out now that's for sure